In a process of manufacturing an electronic device such as a semiconductor device, plasma processing may be performed on a target object by using a plasma processing apparatus. In the plasma processing, it is required to suppress generation of particles that may cause a product defect.
The particles may be generated from an inner wall surface of the plasma processing apparatus which defines a processing space where a plasma is generated. A solution to suppress the generation of particles from the inner wall surface is to exchange a member that provides the inner wall surface at a regular interval. Another solution to suppress the generation of particles from the inner wall surface is to form a film on the inner wall surface before the plasma processing is performed on the target object. The latter solution, i.e., the technique for forming a film on the inner wall surface before the plasma processing of the target object, is disclosed in Japanese Patent Application Publication Nos. 2014-53644 and 2007-165479, and U.S. Pat. No. 7,204,913.
A plasma etching process is an example of the plasma processing. The plasma etching process is performed to transfer a pattern of a mask on an etching target film to the etching target film. Generally, a resist mask is used as a mask. The resist mask is formed by a photolithography technique. Therefore, a critical dimension of the pattern formed on the etching target film depends on a resolution of the resist mask formed by the photolithography technique. However, the resolution of the resist mask has a limitation. In other words, there is a resolution limit.
Meanwhile, a demand for high integration of electronic device is increasing and it is required to form a pattern smaller than the resolution limit of the resist mask. Therefore, as disclosed in Japanese Patent Application Publication No. 2011-82560, there is suggested a technique for adjusting a size of a resist mask by forming a silicon oxide film on the resist mask and reducing a width of an opening formed by the resist mask.
In the plasma etching using the mask having a size adjusted as described above, the generation of particles needs to be suppressed. Therefore, it is required to form a film on the inner wall surface of the plasma processing apparatus. The film is not necessarily formed on the entire inner wall surface, but may be selectively formed on the inner wall surface. It is also required to prevent a period of time for processing the target object from being increased by the film formation. In other words, the decrease of the throughput needs to be suppressed.
Accordingly, in processing the target object which includes the adjustment of the size of the mask, it is required to selectively form a film on the inner wall surface of the plasma processing apparatus and prevent the decrease of the throughput.